The present invention is directed to a longitudinal water-tight waveguide cable in which at least one fiber-shaped waveguide is arranged in an interior of a protective sheath and the remaining inside space of the sheath is filled with a gel-like substance.
A longitudinal water-tight light waveguide cable is disclosed in German O.S. No. 27 28 642, and the cable has a sheath containing at least one optical waveguide such as a fiber which is supported in the sheath by a viscous substance which will no longer flow or drip from the sheath. The substance is formed by weakly cross-linking silicone resins, polyester resins, thermoplastics, polyeurethane rubbers or expanded polystyrol in oil. A good longitudinal water tightness can be achieved with the light waveguide cables constructed in this manner.
However, it should also be assured that the substance which serves as the filling compound does not create tensile forces or pressure forces on the light waveguides since attenuation of the light waveguide conductors would otherwise be increased due to the application of such forces. In order to achieve this with the cross-linking filling compounds of the above-mentioned reference, a relatively high portion of softeners must be used.
In general, when utilizing a cable filling compound for light waveguide cables, there exists a problem that the filling substance for the filling compound should be sufficiently thin bodied or fluid during the filling operation in order to either simplify or make possible the step of filling the substance into the sheath of the cable. A largely-temperature independent gel-like consistency is to be achieved in the filled cable in order to avoid the creation of tensile or pressure forces which would increase the attenuation in the light waveguide. Moreover, there is a demand that the substance employed as the filling compound should be easy to manipulate and be economical.